I. Field of the Invention
The present invention is directed primarily to truck bodies designed specifically for refuse hauling trucks and, more particularly, to an improved packing and ejection mechanism control system for rear loading, rear discharging refuse truck bodies which enables the front-to-rear packing density of packed material to be varied within a load to thereby shift more of the refuse weight forward in the storage compartment of the refuse truck body to achieve improved load balance.
II. Related Art
Refuse collection trucks commonly include a truck chassis fitted with a distinctly configured body specifically designed for receiving, compacting, hauling and discharging refuse materials and including all of the associated operated mechanisms. One very successful design of refuse hauling truck bodies is known as a xe2x80x9crear loaderxe2x80x9d and includes a refuse hauling reservoir accessible for loading and discharging from the rear of the vehicle. This system includes a hydraulic compacting mechanism which repeatedly compacts the refuse after each loading. In this manner refuse eventually fills the available or useable reservoir volume extending from the front end back toward the rear of the body until no more material can be compacted. The forward wall against which the refuse is compacted in a typical rear loading refuse truck body also is the packing/ejection panel of a cylinder-operated ejection mechanism which, in effect, during an ejection cycle moves the panel aft on a horizontal plane in the manner, of a plow to expel the entire contents of the refuse volume during ejection. Typically, the bottom portion of the ejection mechanism is supported on a plurality of load bearing sliders carried by rails and adapted to slidably support the ejector system just above the truck body floor. The ejector system is operated by a hydraulic cylinder which typically mounts in the front of the truck body and is connected to the rear portion of the ejector panel, i.e., behind the face of the panel. By way of definition, this cylinder is referred to as the packing cylinder, ejection cylinder and packing/ejection cylinder. Likewise, the ejector panel may be referred to as the packing panel. These names arise from the fact that refuse is packed against the packing or ejector panel and the resistance of the packing or ejector panel to being pushed back is controlled by the packing/ejection cylinder.
The operation of the cylinder to position the ejector system is two-fold. When the cylinder is fully retracted the ejector is in the fully forward position as when the truck is fully loaded with refuse. When the cylinder is fully extended the ejector mechanism if moved fully aft to the truck body to a position where refuse will be completely expelled. At the beginning of the packing operation with the reservoir empty, the ejection mechanism and panel are positioned in the rearward portion of the truck body with the ejector mechanism exhibiting a preset resistance to retreating toward the forward end of the body. This is accomplished by controls which adjust the pressure in the ejection cylinder to a predetermined fixed amount. As this is exceeded, fluid is expelled from the cylinder and the piston rod retracts. This causes the ejection mechanism to retreat toward the front of the truck body as it is pushed ahead of the packed refuse against a constant resistance until the truck body is fully filled which, more or less, produces a load of substantially uniform packing density.
A rear loading, rear-discharging refuse body packing density control typically is one in which the hydraulic system is provided with a tailgate/ejector spool valve assembly which is typically located on the left or right front of the rear loader body and which has a dedicated open center sensing hydraulic cartridge in the ejector valve work section to control the ejector cylinder pressure. Other rear loader hydraulic systems use separate manifold assemblies to sense pressures within the packing cylinder. As previously indicated, all of these systems attempt to maintain a constant density in the refuse throughout the entire load.
A common problem with rear loading, rear discharging refuse packers of the class involves the weight distribution of the load. The packing process is designed to pack the load to a substantially uniform density from front to rear. However, rear loaders have a heavy tailgate assembly and large hopper for loading refuse that are located aft of the rear wheels of the chassis. The rear loader tailgate typically also contains large hydraulic spool valves, controls, slide and sweep assemblies and four large hydraulic cylinders to operate slide and sweep functions of the packing sequence. The rear loader tailgate may also carry optional devices such as cart tippers, tipper bars, winches and other accessories installed requiring yet more additional hydraulics and controls thereby adding still more weight aft. All of these components add to the weight of the rear loader tailgate and can cause the total tailgate weight to approach 10,000 lbs. (4,535 kg.) on some models. The added weight behind the chassis rear wheels makes it difficult for the front axle to reach or come close to its legally allowed gross front axle weight limit when the packer is loaded by the time the rear axles reach their gross weight rating. At that time, the rear loader has packed its maximum allowable payload even though the front axle may not be fully loaded or the body reservoir completely full. When the rear axles of the rear loader are at the maximum legal payload, the rear loader driver must leave the route and travel to the transfer station or landfill to unload.
Thus, there has existed a definite need to shift additional weight forward in the packer body storage reservoir so that more of the load is carried by the front axle so that the front axle will approach the gross weight limit when the rear axles are at the gross weight limit thus permitting trucks of the rear loader class to legally transport a greater total payload.
By means of the present invention there is provided a packing control system for a rear loading, rear discharge refuse packing body that enables adjustability in the overall weight distribution of the packed refuse. The packing density control system of the invention involves controlling the resistance of the packing/ejection panel against which refuse is packed in a rear loading refuse collection truck body so that the force necessary to cause the panel to retreat toward the front of the truck as refuse is packed in front of it can be varied in accordance with the desired density of the load as it is packed.
The variable packing density control system of the invention uses a detection system to sense the position of the packer/ejection panel within the vehicle and uses this information to control the pressure in the ejection cylinder which determines the resistance of the packing/ejection panel to the material being packed against it. Preferably, the system is controlled such that refuse material packed closest to the packing/ejection panel is subjected to higher packing force and thereby achieves a higher packing density. This translates to a higher packing density in the forward portion of the load when the packing/ejection panel retreats to its fully loaded position at the front of the refuse collection body.
In one preferred embodiment, the system utilizes one or more proximity or mechanical switches to sense angular position of the ejection cylinder which is normally attached between the forward portion of the refuse container body and the packing/ejection panel in a top-to-bottom relation which angle increases as the packing/ejection panel retreats toward the front of the refuse container body before the mass of packed refuse. When this angle reaches certain predetermined value, the packing density is switched usually from a higher to a lower amount in accordance with hydraulic control valve settings. It is also possible to use a system which modulates the pressure as the packing/ejection panel retreats to gradually change the packing density.
In this manner, the densest part of the load is shifted to the front of the refuse container body and therefore additional weight is transferred from the rear axles to the front axle thereby increasing the nominal capacity of the refuse vehicle by as much as about a ton.